Trigonometric Identities not on Formula Sheet

trigonometric identities to learn

Identities: sin^{2} x + cos^{2} x

sin^{2} x + cos^{2} x \equiv 1

Identities: 1 + tan^{2} x

1 + tan^{2} x \equiv sec^{2} x

Identities: 1 + cot^{2} x

1 + cot^{2} x \equiv cosec^{2} x

Double Angle Formulae: sin 2x

sin 2x \equiv 2 sin x cos x

Double Angle Formulae: cos 2x (Cos identity)

cos 2x \equiv 2 cos^{2} x - 1

Double Angle Formulae: cos 2x (Sec identity)

cos 2x \equiv 1 - 2 sin^{2} x